Apparatus for reforming rod-shaped and/or tubular, electrically conductive materials

ABSTRACT

An apparatus for reforming rod-shaped and/or tubular, electrically conductive and/or magnetizable materials, in particular for drawing or extruding: the apparatus has an inductor of an electric linear motor, by means of which a traveling electromagnetic field can be produced; the inductor includes coils which are arranged axially next to one another; the coils form a channel; the apparatus includes one or more means for conducting a magnetic flux which are arranged in the channel such that they can be removed.

BACKGROUND OF THE INVENTION

The invention relates to an apparatus for reforming rod-shaped and/ortubular, electrically conductive and possibly magnetizable materials, inparticular to an apparatus for drawing or extruding.

The patent specification having the number U.S. Pat. No. 3,911,706 Adiscloses an apparatus of the type mentioned initially which has aninductor of an electric linear motor. This inductor has coils, which arearranged axially next to one another such that the center of the coilswhich remains free forms a channel. The rod-shaped or tubular material,which is to be reformed and which is electrically conductive andpossibly magnetizable, is introduced into this channel. This materialthen forms the armature of the linear motor. Owing to the fact that atraveling magnetic field is produced in the channel of the inductor, thearmature, i.e. the material to be reformed, is moved on in the channel.In the process, with appropriate conductance of the inductor, thematerial to be reformed can be moved through the die of an apparatus ofthe type mentioned initially, as a result of which the material isreformed.

The abovementioned document having the patent number U.S. Pat. No.3,911,706 A discloses a linear drawing machine for drawing a rod-shapedmaterial through the die of a female mold. For this purpose, theinductor is arranged such that it lies downstream of the die in thedrawing direction. The rod-shaped material which is inserted into thedie in a manner which is not disclosed in any more detail is passedthrough the inductor downstream of the die in the drawing direction, asa result of which the inductor, interacting with the rod-shaped drawingmaterial which acts as the armature, forms a linear motor which drawsthe rod-shaped drawing material through the die and thus brings aboutthe required force for the reforming process.

The disadvantage of the drawing apparatus disclosed in theabovementioned document is the fact that the forces produced by theinductor interacting with the drawing material are only sufficient for areforming process, in particular for larger drawing materials, if theinductor has a length of several 100 m. Such a drawing machine, however,is unrealistic since it cannot be produced and operated at reasonablecost.

A further disadvantage is the fact that, owing to the channel sizeprescribed by the inductor, the apparatus is only designed for drawingmaterials of one diameter or of one range of diameters.

The present invention was therefore based on the object of developing anapparatus for reforming tubular or rod-shaped drawing material of thetype mentioned initially such that forces can be brought about evenusing smaller machines in order to achieve reforming of the tubular orrod-shaped material. In addition, the apparatus will also be suitablefor drawing materials having different diameters or different ranges ofdiameters.

SUMMARY OF THE INVENTION

Accordingly, an apparatus according to the invention for reformingrod-shaped and/or tubular materials has one or more means for conductinga magnetic flux which are arranged in the channel such that they can beremoved.

Tests on a reforming apparatus of the type mentioned initially haveshown that the magnetic flux is not conducted in optimum fashion in orthrough the tubular or rod-shaped material to be reformed for optimumforce to be produced which acts on the material to be reformed in orderto move it. This could be attributed to air gaps which remain, forexample, between the inner wall of the channel and the outer surface ofthe material to be reformed. Experiments have now shown that, byintroducing a means for conducting the magnetic flux into the channel,the magnetic flux in the tubular or rod-shaped material to be reformedis combined such that the force which acts on the material to bereformed can be increased by a factor greater than 10. It is thus thenpossible to achieve a considerable reduction in the physical size of theapparatus of the type mentioned initially. An apparatus according to theinvention is as a result more compact and can be operated in asignificantly more cost-effective manner.

An apparatus according to the invention may have a tube as a first meansfor conducting the magnetic flux. This tube may have first sections madeof a magnetizable, in particular soft-magnetic material and secondsections made of a non-magnetizable or comparatively only weaklymagnetizable material. In this case, the sections are advantageously inthe form of sleeves. The sections of a tube of an apparatus according tothe invention are arranged coaxially next to one another. The sectionsthus together form the tube.

The material of the first sections of an apparatus according to theinvention may be a metal, in particular iron, or else a material whichcontains metal and in particular iron. The material may also be cobalt,nickel or cobalt, nickel or iron alloys. The material advantageously hasa high saturation field strength. The material may be a powder metal.The material may likewise be powder-sintered or composed of laminatedlayers. It may likewise be provided with slots in the longitudinaldirection.

The material from which the second sections are produced mayadvantageously be a plastic.

The alternate arrangement of the sections makes it possible for themagnetic flux to be passed, in combined form, to the material to bereformed.

The tube must have an outer diameter which is not larger than the innerdiameter of the channel, such that it is possible to insert the tube inthe channel. However, the outer diameter is advantageously the same sizeas or only slightly smaller than the diameter of the channel. Inaddition, the tube has an inner diameter which is slightly larger thanthe material to be reformed. Overall, it should be possible for the airgap, which is between the inner wall of the channel and the material tobe reformed, to be as small as possible and to be filled as much aspossible with the means for conducting the magnetic flux.

The inductor of an apparatus according to the invention may includeperforated disks, which are arranged between the coils coaxially withrespect to the coils and which form, together with the coils, thechannel of the inductor. The disks make it possible for the magneticflux, which is produced by the coils of the inductor, to be combinedeven in the regions between the coils. The disks may have a radial slot.If the disks are provided in the case of the inductor, it isadvantageous if the second sections of the tube have a width whichcorresponds to the width of the coils. The tube is advantageously pushedinto the inductor such that the second sections are aligned with thecoils and the first sections are aligned with the disks.

In the case of tubular materials, it has also been shown that the cavitywithin the tube leads to the magnetic flux not being passed through thetubular material to be reformed in optimum fashion. If, instead, asecond means for conducting the magnetic flux in the form of a cylinderis introduced into the inductor of an apparatus of the type mentionedinitially, this leads to the flux being conducted through the tubularmaterial to be reformed with an optimum alignment. The cylinder, whichis arranged in the inductor as the second means for conducting themagnetic flux, is advantageously arranged in the channel coaxially withrespect to the coils.

The cylinder of an apparatus according to the invention isadvantageously dimensioned such that a gap which is as small as possibleremains between the cylinder and an inner wall face of the channel orthe inner wall face of the first means for the purpose of inserting andpassing through the tubular material to be reformed.

According to the invention, the cylinder may be a hollow cylinder.

The cylinder is advantageously produced from a material which includes ametal, in particular iron. The material may also be cobalt, nickel orcobalt, nickel or iron alloys. The material advantageously has a highsaturation field strength. In addition, it is possible for the cylinderto be produced from a powder metal. The material may likewise bepowder-sintered or composed of laminated layers. It may likewise beprovided with slots in the longitudinal direction.

The cylinder can be retained on the drawing mandrel, for example, bymeans of mechanical and/or electromagnetic retaining means. The cylindermade of a soft-magnetic and ferromagnetic material may be retained, forexample, by the coils of the inductor or further coils, the coils havingan alternating current or a direct current flowing through them.

It is advantageously possible with an apparatus according to theinvention to produce a traveling electromagnetic field which has amagnetic flux density having a gradient in the axial direction of thechannel which has an amplitude of greater than B=1 T. The electricalcurrent density which can be produced by the coils of the inductor isadvantageously greater than J=10 A/mm².

At least some of the coils may have conductors which have a resistivityof ρ=0.017×10⁻⁶ Ωm or less. At least some of the coils may haveconductors which are superconductive. The superconductive conductors ofsuch coils may be made of a material which has a critical temperature ofgreater than T=77 K.

BRIEF DESCRIPTION OF THE DRAWING

An exemplary embodiment of an inductor of an apparatus according to theinvention is described in more detail with reference to the drawing, inwhich:

FIG. 1 shows the inductor according to the invention having a first anda second conducting means and a tubular drawing material.

DETAILED DESCRIPTION OF THE INVENTION

The inductor 1 according to the invention and illustrated in FIG. 1 of alinear motor has coils 3, which are arranged coaxially next to oneanother. Perforated disks 6, which cover the outer edge of the coils,are arranged between these coils 3. The disks cover the coils 3 suchthat the protruding edge of the disks 6 ends flush with the coil. Thedisk 6 and the coil 3 embedded therein thus form a body which forms aring having a rectangular cross section. If these bodies comprising thedisk 6 and the coil 3 are arranged next to one another, as a result thecoils are completely, with the exception of on the inside, enclosed bythe directly associated disk 6 or an adjacent disk 6.

The coils 3 and the disks 6 together form a channel, through which thematerial 2 to be reformed is transported. The transport takes place inthis case by means of forces which act on the material 2 owing toelectromagnetic induction and mutual induction.

The disks 6 are produced from a powder metal. The disks serve thepurpose of combining and conducting the magnetic flux produced by thecoils.

If the material to be reformed is now introduced into the channel, andthis material 2 to be reformed has an outer diameter which isconsiderably smaller than the inner diameter of the channel, this leadsto the magnetic flux partially being conducted through the remaining airgap between the material 2 to be reformed and the inner wall of thechannel and not through the material 2 to be reformed itself.

In order to prevent this, the first means 4 is pushed into the channel.In this case, a tube 4 is used, which comprises first sections 4 a andsecond sections 4 b, which are in the form of sleeves and which arearranged coaxially next to one another such that they form a tube. Thistube has an outer diameter which corresponds to the inner diameter ofthe channel. The inner diameter of the tube, on the other hand,corresponds approximately to the outer diameter of the material 2 to bereformed. The first sections 4 a of the tube 4 are likewise producedfrom a powder metal. These first sections can thus combine and conductthe magnetic flux which is produced by the coils 3 in the same manner asthe disks 6. The second sections 4 b, on the other hand, are producedfrom a plastic. These sections 4 b cannot combine the magnetic flux. Aslong as the tube 4 is pushed into the channel, the first sections 4 a ofthe tube 4 form a bridge over the otherwise remaining air gap, whichleads to optimum guidance of the magnetic flux. The magnetic flux can beintroduced into the material 2 to be reformed in combined form.

The material to be reformed which is illustrated in FIG. 1 is a tubularmaterial 2. The interior which remains free in the tubular material 2 islikewise not optimal for the production of the force which acts on thematerial 2 to be reformed. According to the invention, a secondconducting means has therefore been inserted into the channel. Thissecond means is formed by a cylinder 5 which has a diameter which issmaller than the inner diameter of the material to be reformed. As longas the material 2 to be reformed has not inserted into the channel, agap would thus remain between the cylinder 5 and the tube 4 or the innerwall of the channel, and a tubular material to be reformed can beinserted into this gap. The cylinder 5, which may also be a hollowcylinder, is likewise produced from a powder metal, and the cylinderresults, as is also the case for the first sections 4 a and the disks 6,in a combined magnetic flux. This makes it possible for the magneticflux to flow essentially radially through the tubular material 2 to bereformed, which is optimal for force production.

1. An apparatus for reforming rod-shaped and/or tubular, electricallyconductive and/or magnetizable materials, for drawing or extruding: theapparatus has an inductor of an electric linear motor, by means of whicha traveling electromagnetic field can be produced; the inductorcomprises coils which are arranged axially next to one another; thecoils form a channel; the apparatus further comprises one or more meansfor conducting a magnetic flux which are arranged in the channel suchthat they can be removed.
 2. The apparatus as claimed in claim 1,wherein a first conducting means is a tube.
 3. The apparatus as claimedin claim 2, wherein the tube has first sections made of a magnetizablematerial and second sections made of a non-magnetizable or only weaklymagnetizable material.
 4. The apparatus as claimed in claim 3, whereinthe first and second sections are in the form of sleeves.
 5. Theapparatus as claimed in claim 3, wherein the first and second sectionsare arranged coaxially next to one another.
 6. The apparatus as claimedin claim 3, wherein the material of the first sections is or contains asoft-magnetic metal or iron.
 7. The apparatus as claimed in claim 3,wherein the material of the second section is a plastic.
 8. Theapparatus as claimed in claim 3, wherein the tube has an outer diameterwhich is the same size as or slightly smaller than a diameter of thechannel.
 9. The apparatus as claimed in claim 2, wherein the tube has aninner diameter which is slightly larger than the material to bereformed.
 10. The apparatus as claimed in claim 1, wherein the inductorcomprises disks (6), which are arranged between the coils coaxially withrespect to the coils and which form, with the coils, the channel. 11.The apparatus as claimed in claim 10, wherein a first conducting meanswith a tube, wherein the tube has first sections and second sections,the second sections of the tube have a width which corresponds to thewidth of the coils or is smaller than this width.
 12. The apparatus asclaimed claim 1, wherein a second conducting means is a cylinder. 13.The apparatus as claimed in claim 12, wherein the cylinder is arrangedin the channel coaxially with respect to the coils.
 14. The apparatus asclaimed in claim 13, wherein the apparatus has, between the cylinder andan inner wall face of the channel or of the tube, a gap for insertingand passing through the material to be reformed.
 15. The apparatus asclaimed in claim 12, wherein the cylinder is a hollow cylinder.
 16. Theapparatus as claimed in claim 12, wherein the cylinder is produced froma material which comprises a soft-magnetic metal, or iron.
 17. Theapparatus as claimed in claim 12, wherein the cylinder is a powdermetal, is a powder-sintered metal or is laminated from layers orprovided with longitudinal slots.
 18. The apparatus as claimed in claim1, wherein the inductor is used in the channel to produce a travelingfield with a magnetic flux density having a gradient in the axialdirection of the channel which has an amplitude of greater than B=1 T.19. The apparatus as claimed in claim 1, wherein, when using the coils,electrical current densities of greater than J=10 A/mm² can be produced.20. The apparatus as claimed in claim 1, wherein at least some of thecoils have conductors which have a resistivity of ρ=0.017×10⁻⁶ Ωm orless.
 21. The apparatus as claimed in claim 1, wherein at least some ofthe coils have conductors which are superconductive.
 22. The apparatusas claimed in claim 21, wherein the superconductive conductors are madeof a material which has a critical temperature of greater than T=77 K.23. The apparatus as claimed in claim 12, wherein the cylinder isretained by means of mechanical and/or electromagnetic retaining means.